Does FDA regulate laboratory-developed tests (LDTs) now that the LDT rule has been vacated?

1What happened to FDA’s LDT rule.

On 6 May 2024 FDA published a final rule, effective 5 July 2024, to “make explicit that in vitro diagnostic products (IVDs) are devices” under the FD&C Act “including when the manufacturer of the IVD is a laboratory”. Alongside it, FDA announced it would phase out its general enforcement discretion for laboratory-developed tests over four years.¹

None of those stages took effect. On 31 March 2025, in American Clinical Laboratory Association v. FDA, the US District Court for the Eastern District of Texas granted the laboratories’ motions for summary judgment and ordered: “The final rule is hereby SET ASIDE and VACATED.”² It remanded the matter to the Secretary of Health and Human Services for further consideration.³

On 19 September 2025 FDA published a final rule, effective the same day, removing the words “including when the manufacturer of these products is a laboratory” from 21 CFR 809.3(a) and reverting to the text as it stood before the 2024 rule. FDA called the action “ministerial”, since the court had already vacated the rule, and issued it without notice and comment.³ FDA’s LDT page now lists the 2024 rule as vacated.⁴

2What the court decided.

The court held that the rule “exceeds FDA’s statutory authority”. In its reading of the FD&C Act, FDA may regulate manufacturers of commercially distributed devices, “including devices used to perform standardized clinical tests (known as ‘test kits’)”. But “laboratory-developed test services are professional medical services that are qualitatively and categorically different from the tangible goods that FDA may regulate as ‘devices’”.²

The court described these services as in-house diagnostic tests “developed, validated, and performed by trained professionals within a single clinical laboratory”, at the request of a physician. It noted that they have long been regulated by the states and by CMS under the Clinical Laboratory Improvement Amendments of 1988 (CLIA).²

3What counts as an LDT.

In the 2024 rule, FDA said it had generally considered an LDT to be an IVD “intended for clinical use and that is designed, manufactured, and used within a single laboratory” that is CLIA-certified and meets CLIA’s requirements for high complexity testing. Since the Medical Device Amendments of 1976, FDA had exercised enforcement discretion so that it “generally has not enforced applicable requirements with respect to most LDTs”.¹

The definition that remains in force, 21 CFR 809.3(a), says IVDs are “reagents, instruments, and systems intended for use in the diagnosis of disease or other conditions”, and that these products “are devices” under the FD&C Act and may also be biological products under section 351 of the Public Health Service Act.⁵

4Who regulates LDTs now.

CMS regulates laboratory testing performed on humans in the US for health assessment or to diagnose, prevent or treat disease, through the CLIA programme. CLIA’s requirements become more stringent as a test becomes more complex, and the programme covers about 320,000 laboratory entities.⁶ A laboratory is out of compliance unless it holds a current CLIA certificate for the category of testing it performs, or is CLIA-exempt. The rules do not apply to forensic testing, or to research laboratories that do not report patient-specific results.⁷

For a test the laboratory developed or modified, 42 CFR 493.1253(b)(2) applies. A laboratory that modifies an FDA-cleared or approved test system, or introduces one not subject to FDA clearance or approval, “including methods developed in-house”, must establish these performance specifications, as applicable, before reporting patient results:⁷

• accuracy;
• precision;
• analytical sensitivity;
• analytical specificity, including interfering substances;
• the reportable range of test results;
• reference intervals (normal values);
• any other performance characteristic required for test performance.

The laboratory then sets its calibration and control procedures from those specifications and must document all of it.⁷ A test that does not appear on the published lists of categorised tests is treated as high complexity until it is reviewed.⁸

5What FDA still regulates.

The ruling concerned laboratory-developed test services. IVDs remain devices under 21 CFR 809.3(a), and the court accepted FDA’s authority over commercially distributed test kits.⁵² A company that makes IVD reagents, instruments or kits for sale to laboratories therefore still works under FDA’s device requirements, including the Quality Management System Regulation in Part 820.

6What the 2024 rule means now.

Anything written about the 2024 rule as a coming requirement is out of date. The rule was vacated before its first stage, due in May 2025, could begin, and the regulation text has been restored.²³ Its preamble remains a record of FDA’s position, but it imposes nothing.

7How it runs in Seal.

Seal does not decide which regime a test falls under. It keeps the evidence a laboratory needs either way. In Seal’s LIMS, each result is captured with its sample, method version, specification and instrument file, and a method change carries its impact assessment and verification while earlier runs keep the version they used. Methods developed in Seal’s ELN come into routine testing as an approved version with defined parameters, calculations and review requirements.

Laboratories that test for clients can keep each client’s records apart behind its own boundary, as the contract laboratory blueprint describes. For IVD manufacturers whose kits are devices, the medical device blueprint links each requirement to its design output, verification and risk controls, and the same structure serves IVDR technical documentation.